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This mechanism supports extensibility; implementations of future versions 077 * of the HTTP protocol might apply these directives to header fields not defined in HTTP/1.1. 078 * 079 * <p> 080 * The cache-control directives can be broken down into these general categories: 081 * <ul> 082 * <li>Restrictions on what are cacheable; these may only be imposed by the origin server. 083 * <li>Restrictions on what may be stored by a cache; these may be imposed by either the origin server or the user 084 * agent. 085 * <li>Modifications of the basic expiration mechanism; these may be imposed by either the origin server or the 086 * user agent. 087 * <li>Controls over cache revalidation and reload; these may only be imposed by a user agent. 088 * <li>Control over transformation of entities. 089 * <li>Extensions to the caching system. 090 * </ul> 091 * 092 * <h5 class='section'>See Also:</h5> 093 * <ul class='doctree'> 094 * <li class='extlink'>{@doc RFC2616} 095 * </ul> 096 */ 097@Header("Cache-Control") 098public final class CacheControl extends HeaderString { 099 100 /** 101 * Returns a parsed <code>Cache-Control</code> header. 102 * 103 * @param value The <code>Cache-Control</code> header string. 104 * @return The parsed <code>Cache-Control</code> header, or <jk>null</jk> if the string was null. 105 */ 106 public static CacheControl forString(String value) { 107 if (value == null) 108 return null; 109 return new CacheControl(value); 110 } 111 112 private CacheControl(String value) { 113 super(value); 114 } 115}